This invention relates to waste treatment systems, and in particular, to a method for removing nitrogen and recovering ammonia content from waste streams with high concentrations of nitrogen, a portion of which is organically bound nitrogen, such as in the supernatant of anaerobically digested sludge, landfill leachate or industrial wastewaters. The method is comprised of a biological process (aerobic or anaerobic), followed by a physico-chemical process and, in some cases, followed by an aerobic biological process.
An example of an application for the present invention process with an aerobic first step is for municipal wastewater treatment plants with anaerobic digestion. The supernatant from the anaerobic digestion of blended or secondary sludge contains high concentrations of ammonium that, as a recycle stream to the influent of a wastewater treatment plant, may account for as much as 17-20% of the nitrogen loading to the plant. This waste stream together with other nitrogen rich recycles may contribute 20-30% of total nitrogen load to the plant. These recycle streams introduce additional difficulty to treatment, within the main plant, because (1) they typically do not contain the requisite carbon to nitrogen ratio (C/N) for traditional biological nitrogen removal; and (2) they are generated by sludge handling operations that typically do not occur every day and, therefore, result in shock loads to the main plant. However, the increasingly stringent nutrient limits being applied to wastewater treatment plants require management of these recycle streams in order to consistently achieve low effluent nitrogen concentrations.